Combustion engine with overhead camshafts

ABSTRACT

A combustion engine is provided with overhead camshafts. The camshafts are mounted in bearings. The cylinder head with camshafts is fixed on a cylinder block via cylinder head screws. Bearing caps are fixed on the cylinder head via bearing cap screws. Each bearing cap comprises three openings for bearing cap screws and additionally a fourth opening for a cylinder head screw.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No. 102010051367.9, filed Nov. 13, 2010, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The technical field relates to a combustion engine with overhead camshafts. The camshafts are mounted in bearings, each of which comprises a lower bearing half shell as integral part of a cylinder head and an upper bearing half shell as integral part of a bearing cap. The cylinder head with camshafts is fixed on a cylinder block via cylinder head screws. The bearing caps are fixed on the cylinder head via bearing cap screws.

BACKGROUND

From the publication DE 35 41 700 A1 a combustion engine with at least one overhead camshaft is known. The bearing points of this camshaft are fastened to the cylinder head by means of bearing caps. There, one of the two bearing cap screws required is designed as hollow screw, through the axial through-bore of which a screw serving for the fastening of the cylinder head on the cylinder block can be passed.

Because of this it is possible to preassemble the cylinder head with the camshaft as a unit and then fasten this unit through the cylinder head screws, which are partially guided in the axial through-bores of the bearing cap screws. Thus, a retightening of the cylinder head screws and an assembly of the cylinder head can be carried out without prior disassembly of the camshaft. For the preassembly of the cylinder head unit of cylinder head, camshaft and bearing caps non-standardized hollow screws are required for this purpose in order to fix the bearing caps on the cylinder head and thus the camshaft on the cylinder head. For the cylinder head screws for fixing the cylinder head on the cylinder block, special screws with non-standardized screw heads are also required in order to be able to assemble these through the hollow screws using suitable special tools.

At least one object is to create a combustion engine with overhead camshafts, where both the cylinder head unit of camshafts and camshaft bearings as well as the engine block with cylinder block and screwed-on cylinder head unit have standardized screw connections. In addition, other objects, other desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.

SUMMARY

In an embodiment of the combustion engine with overhead camshafts the camshafts are mounted in bearings. The cylinder head with camshafts is fixed on a cylinder block via cylinder head screws. Bearing caps are fixed on the cylinder head via bearing cap screws. Each bearing cap has three openings for bearing cap screws and additionally a fourth opening for a cylinder head screw.

The advantage of such a combustion engine is that a cylinder head unit, which already comprises the camshafts, through the fixing of the bearing caps with the help of three bearing cap screws each can be preassembled independently of the cylinder head assembly. Furthermore, this combustion engine has the advantage that despite the spatial constriction through the camshafts preassembled on the cylinder head it is possible to assemble or disassemble this cylinder head unit on the cylinder block as a unit if required using standard screw connections, without having to remove the individual bearing caps and camshafts from the cylinder head in order to get to the screw connections of the cylinder head to the cylinder block.

This is achieved in that each of the bearing caps comprises not only the conventional two openings for the bearing cap screws, but three openings. Because of this it is possible on one of the ends of the bearing caps between two bearing cap screws to additionally provide a fourth opening through which the cylinder head can be connected to the cylinder block via a cylinder head screw. Thus it is possible to fix the cylinder head region for each cylinder of the cylinder block in the immediate vicinity of the valve opening through suitable cylinder head screws and thus evenly distribute the contact pressure for the cylinder head gasket over the cylinder head unit. Here it is provided to provide a lower bearing half shell of the camshaft bearing as integral part of a cylinder head and an upper bearing half shell as integral part of cylinder head bearing cap.

It is furthermore provided to arrange on a first end of the bearing cap a first opening for a first bearing cap screw and located opposite, on a second end of the bearing cap, to arrange a second and third opening for bearing cap screws and between the second and the third opening the fourth opening. With such a bearing cap a secure plain bearing mounting of the camshafts can be achieved, where through the arranging of two openings on the second end of the bearing cap in the manner that the fourth opening for a cylinder head screw is arranged in the middle and the second and third opening are arranged symmetrically to the middle opening, an even distribution of cylinder head screws in the middle region of the cylinder head can be guaranteed, while in the outer regions or marginal regions of the cylinder head the positions of the cylinder head screws can be provided outside the regions of the bearing caps. Thus, an even distribution of cylinder head screws in the middle region and in the two marginal regions of the cylinder head is obtained.

In a further embodiment, the openings are arranged in the bearing cap in the shape of a Y. The first end with the first bearing cap screw forms a foot of the Y-shape and the second and the third opening are arranged on the ends of the Y-shape. In a branching position of the Y-shape the fourth opening for the cylinder head screw is provided. Through the Y-shape of the arrangement of the openings in the bearing cap it can be ensured that the loads for the bearing cap are evenly transmitted to the cylinder head and the opening arranged in the branching position does not constitute a weakening of the bearing cap.

In a further embodiment, the first three openings have same diameters, and the fourth opening has a larger diameter than the first three openings. This is an advantage because a screw head of a cylinder head screw can be passed through the fourth of the openings. Here, the fourth opening can be reduced in that as cylinder head screw a screw with internal tool engagement is provided in the screw head, while the three first openings correspond with threaded bores in the cylinder head and merely have to provide adequate free space for inserting the thread portion of the respective bearing cap screw. It was possible to show that for the cylinder heads in production an internal diameter adapted to a shank of M5 or M6 screws is adequate for the first three openings. For the fourth opening, in the branching position of the Y-shape, an internal diameter is provided that is adapted to a screw head of a screw with internal tool engagement in the screw head.

It is furthermore provided that the bearing cap screws and the cylinder head screw are aligned parallel to one another and at a right angle to axes of the camshaft. This rectangular, parallel arrangement facilitates the introduction of threaded bores both in the cylinder head as well as in the cylinder block, but the cylinder head screws can also be introduced at an angle to the axes of the camshaft, if the width of the cylinder head has to be reduced further. On the cylinder head, a first camshaft each for inlet valves and a second camshaft for exhaust valves aligned parallel to the first camshaft are arranged and together with their mounting and the cylinder head form a preassembled cylinder head unit. This preassembled cylinder head unit has the advantage, as already briefly mentioned above, that for the assembly and disassembly the individual bearing caps don't have to be first assembled or disassembled and the camshafts inserted or removed in order for middle cylinder head screws, which connect the cylinder head to the cylinder block, can be screwed on or removed. On the contrary, it is now possible based on the above embodiments through the special configuration of the bearing cap and the fourth opening in the bearing caps to assemble or disassemble the complete cylinder head unit with standard screws, as a result of which assembly time and costs can be reduced both in the production as well as during repair and maintenance.

Furthermore, it is provided that at least two inlet valves and two exhaust valves per cylinder of the cylinder block are provided; where two to three cams next to one another are arranged on the camshafts between two bearing caps in order to securely mount said camshafts. The space requirement of such cams is considerable, more so when many cams have to be provided on the camshafts which are arranged rotationally fixed but axially displaceably on the camshaft in order to vary different opening and closing times of the valves as a function of the vital engine data such as cylinder spacing and cylinder bore with corresponding valve spacing's.

If, as inlet valves, valves of a two-step valve drive are provided, which requires three cams per valve, it becomes clear that the lack of space present on the cylinder head requires that cylinder head screws have to be partially provided below the position of the bearing caps. The use of a valve drive with sliding cams also requires space for the axial displacement travel of the sliding cams so that it is advantageous to partially provide cylinder head screws below the position of the bearing caps and to make possible the access to these cylinder head screws through a fourth opening in the bearing caps.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and:

FIG. 1 shows a schematic cross section through a part region of a combustion engine with overhead camshafts; and

FIG. 2 shows a schematic top view of a camshaft with bearing caps.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description.

FIG. 1 shows a cylinder head 6 which as cylinder head unit 20 is fixed on a cylinder head 9 via a cylinder head gasket 25. The cylinder head unit 20 comprises at least one overhead camshaft 1, which is mounted in a bearing 2. The bearing 2 has a lower bearing half shell 4, which is an integral part of the cylinder head 6. An upper bearing half shell 5 is provided in a bearing cap 7. The bearing cap 7 is connected to the cylinder head 6 with bearing cap screws 11 and 12 via openings 21. The cylinder head 6, with the camshaft 1 and with the bearing 2, forms the cylinder head 20, wherein in the bearing cap 7 a fourth opening 24 is provided, through which access to a cylinder head screw 14 is possible, with which the cylinder head unit 20 via the cylinder head gasket 25 is connected to the cylinder block 9 in a gas-tight and pressure-tight manner. The bearing cap screws 11, 12 and the cylinder head screw 14 are aligned parallel to one another and at a right angle to the axis 8 of the camshaft 1. This rectangular, parallel arrangement facilitates the introduction of threaded bores both in the cylinder head 6 as well as in the cylinder block 9.

FIG. 1 shows only one of the two camshafts 1 with which for example the inlet valves of a two-step valve drive or of a valve drive with sliding cams are equipped. When considering such two-step valve drives it becomes clear that the existing space for three valve drive cams, which are required for each valve with a two-step valve drive, is severely restricted so that cylinder head screws have to be partially provided below the position of the bearing caps. Even when valve drives with sliding cams are employed and displacement travels for the sliding cams have to be provided as a function of the vital engine data such as cylinder spacing, cylinder bore or valve spacing, the lack of space becomes too great so that cylinder head screws 14 have to be partially provided below the position of the bearing caps 7.

In FIG. 1 it is shown that it is possible despite the lack of space to fix a preassembled cylinder head unit 20 via a cylinder head gasket 25 with the help of cylinder head screws 14, without it being necessary to remove the camshaft 1 with the bearing caps 7 from the cylinder head 6 in order to make possible access to the cylinder head screw 14. To assemble the cylinder head unit 20, the cylinder head screw 14 is merely passed through the through-opening in the bearing cap 7 and introduced into a cylinder head bore 26 and finally screwed to the cylinder block 9 with its threaded portion 27.

FIG. 2 shows a schematic top view of a camshaft 1 with bearings 2 and 3, between which cams 17 and 18 are arranged. Of the bearings 2 and 3, merely the upper bearing half shells 5 are partially visible, wherein the bearings 2 and 3 comprise bearing caps 7 in which a first opening 21 is provided on a first end 15 of the bearing cap 7, through which the one bearing cap screw 11 is passed in order to fix the first end 15 of the bearing cap 7 on the cylinder head. Under the screw head of the bearing cap screw 11 a washer 28 is arranged.

A second end 16 of the bearing cap 7 has two openings 22 and 23 for bearing cap screws 12 and 13, so that the bearing cap 7 is securely fixed, wherein the bearing cap screws 11, 12 and 13 are standard M5 screws or standard M6 screws. In addition, a fourth opening 24 is provided in the bearing cap 7 through which a cylinder head screw 14 can be passed in order to connect a preassembled cylinder head unit to the cylinder block.

The shortest connections between the centers of the openings 21 to 24 marked with double dash hyphen dotted line form a Y-shape, wherein on the first end 15 of the bearing cap 7 a first bearing cap screw 11 is fixed to the cylinder head through the first opening 21 and on the ends of the legs 29 and 30 of the Y-shape the second and the third bearing cap screw 12 and 13 are arranged in the openings 22 and 23 respectively. In a central branching position 10 of the Y-shape the fourth opening 24 is finally arranged, through which a cylinder head screw with its screw head 31 can be passed in order to fix the cylinder head unit 20, as it is shown in FIG. 1, on the cylinder block.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. 

1. A combustion engine, comprising: a plurality of bearings; overhead camshafts mounted in the plurality of bearings a cylinder block; a plurality of cylinder head screws; a cylinder head with the overhead camshafts attached to the cylinder block with the plurality of cylinder head screws; a plurality of bearing cap screws; and a plurality of bearing caps that are fixed on the cylinder head with the plurality of bearing cap screws, wherein each bearing cap of the plurality of bearing caps comprise three openings for the plurality of bearing cap screws and s fourth opening for at least one of the plurality of cylinder head screws.
 2. The combustion engine according to claim 1, wherein the plurality of bearings of the overhead camshafts each comprise a lower bearing half shell as an integral part of the cylinder head.
 3. The combustion engine according to claim 1, wherein the plurality of bearings of the overhead camshafts comprise an upper bearing half shell as an integral part of the plurality of bearing caps.
 4. The combustion engine according to claim 1, wherein on a first end of the bearing cap, a first opening for a first bearing cap screw is arranged and located opposite on a second end of the bearing cap, a second opening and a third opening for two bearing caps screws of the plurality of bearing cap screws and the fourth opening arranged between the second opening and the third opening.
 5. The combustion engine according to claim 4, wherein a plurality of openings are Y-shape arranged in the bearing cap, wherein the first end is configured to form a foot of the Y-shape with the first bearing cap screw, wherein the second opening and the third opening are arranged on ends of the Y-shape, and wherein the fourth opening is provided in a branching position of the Y-shape.
 6. The combustion engine according to claim 1, wherein a first three openings of a plurality of openings have a substantially same diameter and the fourth opening has a greater diameter than the substantially same diameter.
 7. The combustion engine according to claim 6, wherein the first three openings of the plurality of openings comprise an inner diameter configured for a shank of M5 screws.
 8. The combustion engine according to claim 6, wherein the first three openings of the plurality of openings comprise an inner diameter configured for a shank of M6 screws.
 9. The combustion engine according to claim 1, wherein the fourth opening comprises an inner diameter that is adapted to a head of a cylinder head screw with an internal tool engagement in the cylinder head screw.
 10. The combustion engine according to claim 9, wherein the plurality of bearing cap screws and the cylinder head screw are aligned substantially parallel and at a right angle to axes of the overhead camshafts.
 11. The combustion engine according to claim 1, wherein a first camshaft each for inlet valves and a second camshaft for exhaust valves aligned parallel to the first camshaft are arranged and assembled as a cylinder head unit on the cylinder head.
 12. The combustion engine according to claim 11, wherein each two inlet valves and two exhaust valves are provided for each cylinder of the cylinder block, and wherein two cams are arranged next to each other camshafts between two bearing caps.
 13. The combustion engine according to claim 1, further comprising sliding cams on camshafts between two bearing caps. 